In math, "over" and "/" and "÷" mean the same thing. The expression you have written is
... 7/12/5/9 = 7/540
It seems possible you may want the ratio of two fractions to be simplified. Perhaps you intend ...
... (7/12)/(5/9) = (7/12)×(9/5) = (7×9)/(12×5) = 63/60
... = 21/20 = 1 1/20
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Dividing by anything is the same as multiplying by its reciprocal. This is a convenient fact when dividing by a fraction.
